This invention relates to structural foundations. It pertains particularly to gas supported building foundations and oil pipe line supports of use particularly in the Arctic where permafrost conditions prevail.
In permafrost areas the erection of buildings is made difficult because of the prevailing permafrost condition of the tundra underlying the building. As the permafrost freezes and thaws with changes in atmospheric conditions, the frozen tundra heaves, sinks and buckles. As a consequence, it is impossible to employ ordinary methods of building construction, as by erecting the building on poured concrete foundation walls, or on a poured concrete floor pad.
To overcome this problem it has been proposed to erect buildings on piling. Here again the permafrost condition of the tundra presents problems of the first magnitude.
The permafrost is hard, so that piling cannot be driven satisfactorily into it. Placing piling in the permafrost disturbs the natural tundra insulation and creates abnormal thawing conditions. As a consequence, the tundra at times melts and forms puddles of mud, which tend not to re-freeze promptly with the result that the piling is not supported adequately.
To overcome this difficulty it has been proposed to install the piling by drilling 15 to 20 feet into the permafrost, installing the piling, placing refrigeration coils about the piling, and freezing the piling in position. Under certain conditions, the piling must be permanently refrigerated to keep them in place.
Accordingly it is apparent that the erection of a piling-supported building in a permafrost area is an exceedingly costly and impractical procedure, the cost under current conditions averaging upwardly of $1,000 per pile plus two months labor charges. Such costs make the installation of piling-supported buildings prohibitive, except in special situations.
It also has been proposed, (Brown et al U.S. Pat. No. 3,734,138) to erect oil pipe lines in permafrost country on pneumatic bag supports whch conform to the original contour of the terrain. However, the proposed supports do not adjust with time to changes in ground level and condition and are not suitable for use in the erection and use of permanent buildings in the Arctic.
It is the general purpose of the present invention to provide structural foundations for use particularly beneath buildings located in permafrost areas, which can be erected at a small fraction of the cost of piling-supported foundations, and which will support the buildings satisfactorily over a long service life under the severe conditions of climate and topographical changes which prevail in the Arctic.
It is another purpose of the present invention to provide a building foundation for use in supporting floor structure which is responsive to varying loads carried by such structures.
Still another object of the present invention is the provision of a building foundation which affords protection from flooding.
Still a further object of the present invention is the provision of a structural foundation which in addition to being low in cost may be installed easily, rapidly and by labor possessing only the usual skills.
A further object of the present invention is the provision of a structural foundation which may be placed on any type of terrain, whether it be soft, boggy, sandy, unstable, or frozen, and which after erection will not rust, rot, nor sustain damage from termites.
The foregoing and other objects of this invention are accomplished by means of a gas-bag supported structural foundation which, generally stated, comprises at least one flexible bag adapted to be arranged on the ground and to support a predetermined structural load; a floor structure superimposed on the bag; and a source of gas under pressure. A conduit system connects the source of pressurized gas to the bags, and the bags to atmosphere. In the conduit system is placed valve means responsive to changes in floor level and operative to direct the flow of gas to and from the bag as required to maintain the floor in a substantially level condition.
In the preferred form of the invention, there are employed a plurality of bags manifolded together in groups in a pattern predetermined to support variable loads to be applied to the floor. In this manner the greatest number or density of bags may be supplied in areas expected to support the greatest load.